The invention relates to an apparatus for illuminating a marking, which is applied on a planar transparent reticle in the form of a diffraction structure.
EP 0 886 163 B1 discloses an optical device having an illuminated reticle. The reticle consists of a planar transparent carrier plate, onto which a marking which is in the form of a diffraction structure is applied. Reticles are used especially in sighting telescopes for marking a target. The marking is located in an intermediate image plane of the sighting telescope. The marking can be applied, in the direction of light of the sighting telescope, on the front or back of the carrier plate.
The marking is illuminated through the edge surface of the carrier plate by a light source which is arranged laterally to the carrier plate. Owing to the action of the diffraction structure, the illuminating beams are directed, in the first order of diffraction, in the direction of the optical axis of the sighting telescope toward the observer, with the result that the marking becomes visible to the observer in the intermediate image.
EP 1 653 271 B1 discloses an illuminating apparatus, with which the illumination of the diffraction structure of the known reticle is improved with the result that greater brightness and greater contrast of the marking in the intermediate image are achieved. The illuminating apparatus consists of a mirror, arranged laterally next to the carrier plate of the marking, having a mirror surface which is curved such that the mirror has two focal points. The light source is located in the region of one focal point. The light beams reflected by the mirror converge toward the marking which is located in the second focal point of the mirror. Depending on the position of the marking on the front or back surface (in the direction of light) of the carrier plate, the light beams are directed onto the marking immediately or after one or more total internal reflections on an inside surface of the carrier plate.
The mirror surface is preferably intended to be arranged on the back of a mirror element onto which light is emitted from the front by the light source. Preferably a light-emitting diode with a prespecified emission wavelength is provided as the light source. The mirror element can be attached to the edge of the carrier plate especially by way of adhesive bonding. The light-emitting diode can be connected to the front of the mirror element.